In memory components, in particular, semi-conductor memory components, a distinction is made between so-called functional memory components (e.g. PLAs, PALS, etc.), and so called tab memory components, e.g. ROM components (ROM=Read Only Memory),—for example PROMS, EPROMs, EEPROMs, and Flash-memories—, and RAM components (RAM=Random Access Memory), e.g. DRAMS or SRAMs.
A RAM component is a memory device in which data is stored under a specific address, from which the data can be read out again later.
Because a RAM component needs to be provided with as many storage cells as possible, it becomes important for the creation of these cells to be kept as simple as possible.
With so-called SRAMs (SRAM=Static Random Access Memory) the individual memory cells for instance consist of a few, e.g. six transistors, and in so-called DRAMs (DRAM=Dynamic Random Access Memory) of only a single suitably controlled capacitance (e.g. the gate source capacitance of a MOSFET), with which in form of a charge one bit at a time can be stored.
In the case of DRAMS, this charge only persists for a short period of time, which means that a so-called “refresh” must be performed regularly, e.g. ca. every 64 ms.
In contrast thereto, in the case of SRAMs, the charge need not to be refreshed, i.e., the respective data remains stored on the cell as long as a respective supply voltage is fed to the SRAM.
ROM components (ROM=Read only memory), for example PROMS, EPROMs, EEPROMs, and Flash-memories, are memory components on which the respective data remains stored even after the respective supply voltage is turned off.
In general, and during the normal use of a ROM component, only read operations are performed, and no write operations.
In order to write data onto ROMs, e.g., PROMS, EPROMs, EEPROMs, etc. (i.e., in order to “program” the ROM), in many cases, special instruments have to be used.
Just as is the case for RAMS, the typical read access times, and the times it takes to write data onto the ROMs may differ between the different types of ROMs.
Due to the above-mentioned differences between e.g. RAM and ROM memory components, etc., and due to the differences mentioned between the different types of e.g. RAMs and ROMs, etc. (and due to further differences not mentioned herein), in general, depending on the particular memory characteristics needed for a particular application, the particular memory component which best fulfills the specific needs of a specific application is chosen for the particular application.
If two or more different memory characteristics are necessary for one and the same application, two or more different types of memory components are used, increasing the seize, the complexity, and the costs of the application.
In addition to the memory components mentioned above, e.g. so-called PMC memory components are known in the art (PMC=programmable metallization cell).
In a PMC memory cell, during the programming of the cell, a metallic dendrite between respective electrodes—depending on whether a logic “1”, or a logic “0” shall be written into the cell—is either built up, or dissolved.
Hence, the contents of the PMC memory cell is defined by the respective resistance between the electrodes.
The resistance between the electrodes is controlled by suitable pulses applied to the electrodes of the PMC memory cell, thereby causing suitable electrochemical reactions which lead to the building up, or dissolution of the abovementioned metallic connection between the electrodes.
PMC memory cells are e.g. disclosed in Y. Hirose, H. Hirose, J. Appl. Phys. 47, 2767 (1975), M. N. Kozicki, M. Yun, L. Hilt, A. Singh, Electrochemical Society Proc., Vol. 99-13, (1999) 298, and e.g. in M. N. Kozicki, M. Yun, S. J. Yang, J. P. Aberouette, J. P. Bird., Superlattices and Microstructures,
Vol. 27, No. 5/6 (2000) 485-488, as well as e.g. M. N. Kozicki, M. Mitkova, J. Zhu, M. Park, C. Gopalan, “Can Solid State Electrochemistry Eliminate the Memory Scaling Quandry”, Proc. VLSI (2002), and e.g. R. Neale: “Micron to look again at non-volatile amorphous memory”, Electronic Engineering Design (2002), etc., the contents of these documents being incorporated herein by reference.